Method of making propeller blades



Jan. 2, 1934. SQUIRES 1,942,221

METHOD OF MAKING PROPELLER BLADES Filed March 11, 1931 V INVENTOR AQ-Mfl ELLE. JED/772 4 /W A ORNEY5- Patented Jan. 2, 1934 UNITED STATES PATENT OFFICE This invention relates to propeller blades such as are employed in connection with propellers of aircrafts and the like, and particularly to an improved method of manufacturing propeller blades.

The main objects of the invention are to provide a method for forming a propeller blade from a sheet-like piece of stock of substantially uniform thickness; to provide a method of this kind in which the sheet-like piece of stock is initially formed into a planular blank of non-uniform width and substantially equal in dimension, at successive cross sections,-to the inner perimeter of the finished product at corresponding cross sections; to provide suitable operations in a method of this character for modifying the planular blank into a tubular blank of circular cross section and non-uniform diameter with the opposite edges of the planular blank in abutting relationship; to provide for the formation of a tubular propeller blade blank of non-uniform cross section from a planular blank, or piece of stock, of the above contour so as to obviate the formation of longitudinal wrinkles in the interior of the tubular blank and the formation of a rough exterior by the gathering of metal during the forming operations heretofore required in bringing a truly cylindrical tube to a tapered formation; to provide suitable welding operations for integrally securing the abutting edge portions together and closing the small end of the tubular blank respectively; and to provide steps in a method of this kind for working the ridges of metal that are formed on the inner and outer sides of the tube during welding of its seam, to the contour of the inner and outer peripheries, respectively, of the tube in a manner which improves the grain structure of the metal and obviates machining of the inner periphery thereof.

Further objects of the invention are to provide an improved propeller blade forming method in which the large extremity of the tubular blank is deformed so as to provide a flange for securement to a propeller hub; to provide a suitable machining operation for modifying the wall thickness of the blank to substantially that desired in the finished product in which the walls of the outer, more tapered end portion of the blank are reduced to a lesser thickness than the remaining portions of the blank and in which the welded seam of the blank is trimmed throughout its entire length; and to provide a final die forming step in this improved method in which the blank is pressed to the desired cross sectional contour with the welded seam thereof located in a position with respect to the dies that causes the seam to lie in a predetermined location in the ultimate blade at which minimum strain occurs.

An illustrative embodiment of the invention is shown in the accompanying drawing, in which:

Fig. 1 is a plan view of a planular blank from 00 which a tubular propeller blade blank is formed.

Fig. 2 is a side elevation of the blank showing the uniform thickness thereof.

Fig. 3 is a transverse section of a pair of die parts illustrating the initial forming operation to 35 which the stock is subjected in making tubular propeller blade blanks.

Fig. 4 is a transverse section of a pair of die parts illustrating the second forming operation involved in producing the tubular blank.

Fig. 5 is a transverse section of a tubular propeller blade blank which is supported on a mandrel, showing the manner in which the seam of the blank is welded.

Fig. 6 is a vertical section taken axially through I; a propeller blade blank showing the latter as it appears after the welding operation.

Fig. 7 is a fragmentary section taken through the axis of the blank shown in Fig. 1, and illustrating the step of deforming the large end of the blank to produce a securing flange.

Fig. 8 is a view similar to Fig. 1 showing the blank as modified in Fig. '1 supported on a mandrel and being machined to bring the wall thickness thereof to desired dimensions.

Fig. 9 is a central vertical section of a propeller blade blank which has been machined to desired dimensions. v

Fig. 10 is a fragmentary vertical section similar to Fig. 9, but illustrating the method of closing the small end of the tube.

Fig. 11 is a transverse vertical section of a tubular blank showing the same positioned between a pair of dies in readiness for compression to final blade shape.

Fig. 12 is a view similar to Fig. 11, but showing the die parts brought together and illustrating the manner in which the cross sectional shape of the blank is modified by the dies.

Fig. 13 is a perspective view of a completed propeller blade illustrating the position in which the welded seam of the blade lies.

The initial step in the present method is to form a tubular blank from a flat sheet metal plate by rolling, bending or otherwise forming the plate to bring its side edges into contacting or substantially contacting relationship, in which position they are secured together by welding. Obviously, the size, shape and contour of the de sired tubular blank will determine the size, shape 110 lindrical form, and an end portion 3 of inwardly tapered formation. To form the particular tubular blank shown, in accordance with the present invention, a planular sheet metal blank 4,

such as is indicated in Figs. 1 and 2, is provided. The contour of the side edges of this sheet, as well as the width thereof, is such that when the blank 4 is brought into tubular shape with the side edges thereof in contact, as in the manner hereinafter described, the resulting product will correspond to the size, shape and contour of the tubular blank desired. The side edges 6 and 7 of the end portion 5 of the blank 4 are slightly arcuate in contour and the widths of successive cross sections of theblank, from one end to the other thereof, are substantially equal to the circumferences of the inner peripheries of corresponding cross sections of the tubular blank 1.

The planular blank 4 may be formed into a tubular blank of the type shown in Fig. 6 in any suitable manner. In the method illustrated in the drawing, the planular piece of stock 4 of predetermined shape and dimensions is placed upon a female die part 8 having a recess 9 of semicircular cross section which corresponds to the contour of one-half of the tube 1 and the laterally intermediate portions of the stock are pressed into the recess by a male die part 10. The male die part 10 imparts to the central portion of the stock 3 which extends longitudinally thereof, the shape of the recess 9 and after the male die part is withdrawn the opposite side portions 11 and 12 of the stock are arcuately bent inwardly until the side edges of the stock abut each other in the manner shown at 13 in Fig. 4. This bending of the side portions 11 and 12 is conveniently accomplished by compressing the stock after it has been modifled to the shape shown in Fig. 3, between the female die part 8 and a substantially identical female die part 14 having a recess 15 registering with and complementary to the recess 9 of the die part 8.

This final forming of the stock to tubular shape may be performed with the aid of a mandrel (not shown) which conforms in size and contour to the internal size and contour of the desired blank. In this case the mandrel is seated in the trough of semi-circular cross section which is produced by the male die part or punch 10 after the latter is removed and the die parts 8 and 14 are forcefully brought together so as to press all areas of the upstanding side portions 11 and 12 of the stock uniformly upon the outer surface of the mandrel and to bring the side edges of the stock into abutting relationship. I

After the blank 4 has been formed into a hollow tube of the desired contour by the above operations or by any other method and suitableapparatus, a mandrel 16, or the like, is inserted into the resulting tube and the abutting edges of the stock are welded together, while the tube is supported on the mandrel, by an electric circuit or in any other convenient way. When the welding process, illustrated in Fig. 5 is employed, electrodes 17 and 18 of an electric circuit (not shown) are applied to the respectively opposite sides of the seam while the blank is passed between rollers 49. The electrical resistance of the metal brings the abutting edges of the seam to the welding temperature and the rollers 49 force the edges together. The edges of the stock are fused together and the fused metal fills in any gap which may have existed therebetween, forming a welded seam 19. Other apparatus may, of course, be employed for carrying out this same type of welding operation, it being understood that I prefer the type shown merely because I have found that a more perfect product generally results, but it is to be understood that other welding methods may be employed where desired.

The ridges of metal which are generally formed on the inner and outer sides of the blank 1 during the welding operation, and are preferably worked by hammering or swaging to conformity with the inner and outer peripheries, respectively, of the tube 1. Working of the metal in this manner produces a grain structure which is desirable in articles of this kind and obviates the necessity of machining the inner periphery of the tube in order to trim the seam.

The tube or blank 1 is then placed in a suitable die such as indicated at 20 in Fig. 7, and is operated upon by a plunger 21 or other suitable apparatus so as to deform the large end of the blank to provide thereon a radially extending annular flange 22 which is used in securing a propeller blade to a propeller hub.

In cases where the above operations have not resulted in a blank having a bore sumciently accurate in size, shape and contour for the purposes thereafter required of it, then such bore may be brought into conformance with a desired standard as follows. The blank may or may not, according to the desires or necessities appearing in the particular case, be brought to a suitable high temperature, and a mandrel, such as that illustrated at 28 in Fig. 8, and having an external size slightly greater than the interior size of the blank 1, may then be forced into it so as to expand it radially a slight amount and preferably stretch it longitudinally a slight amount. This insures the interior size, shape and contour of the blank being brought to conformance with a predetermined standard corresponding with the external dimensions of the mandrel 23.

After completion of this operation, when employed, the blank may be allowed to remain on the mandrel 23, or may be placed on a corresponding one, and the mandrel with the blank 1 thereon is then positioned between suitable centers 24 and 25 in a lathe or other machine, as indicated in Fig. 8, and the blank 1 is externally machined by a tool 26 which is suitably guided in a predetermined path with respect to the external surface of the mandrel 23 so as to bring the wall thickness of the blank to the desired dimensions.

It will be observed that under ordinary conditions the wall thickness of the blank 1, shown in Fig. 6, is slightly greater than the desired maximum thickness of the walls of the finished tubular blank, shown in Fig. 9. In the finished product the maximum wall thickness is at the large end and the wall thickness decreases from the large end of the tubular blank to the small end thereof.

This modification of the wall thickness is accomplished as indicated in Fig. 8, by supporting the blank over its entire length on the mandrel 23 which is in turn supported at both ends between centers. By employing this method it is possible to accurately predetermine the wall thickness of the blank from one end to the other end thereof.

After the blank 1 has been machined to bring its walls to the desired thickness, indicated in Fig. 9, the exterior surface of the blank is smoothed off and preferably brought to a high polish by any suitable operation conveniently employed for such purposes. The blank is next put on a mandrel 27, shown in Fig. 10, which, like the mandrel 23, conforms to the internal size, shape and contour of the blank 1. but which has a rounded small end 28 that is located slightly inwardly from the small end of the blank. The mandrel 27 is mounted in a lathe or other suitable apparatus with the small end of the mandrel and blank supported on a steady-rest 29 and the blank and mandrel are rotated.

A flame 30 from an acetylene or other heating torch is then directed at the small projecting end of the blank 1 until the same is brought to a plastic or semi-plastic condition, and then the projecting end of the blank is spun around the end 28 of the mandrel 27 by a spinning tool 32. By this operation the small open end of the blank 16 is closed and the metal is worked to a single point on the axis of the blank and any possible aperture that might otherwise occur at this point is closed by the metal welding itself. Other methods of closing the small end of the blank may, of course, be employed.

After the small end of the blank is closed, then the blank may be placed between suitable die parts 33 and 34, in the manner illustrated in Fig. 11, with the welded longitudinal seam 19 so located as to throw it into a predetermined location in the finished blade relative to the leading or trailing edges thereof. As a means of illustration I have shown the seam 19 as located in a vertical plane which passes through the central axis of the blank, and on that side thereof which will bring the seam into the center of the pressure face of the propeller, this being one location that I have found desirable in that it lies substantially on the axis of the blade and is therefore subjected to a minimum of stresses. It will be understood that the die parts are provided with cooperating depressions 35 and 36. the combined perimeters of which at any particular cross section of the dies correspond exactly to the perimeter of the blank 1, at that point. The die parts 33 and 34 are then brought together, preferably while maintaining the interior of the blank 1 under suitable pressure and in a heated condition, and thus form the blank to the blade shape shown in Figs. 12 and 13.

Formal changes may be made in the specific embodiment of the invention described without departing from the spirit and substance of the broad invention, the scope of which is commensurate with the appended claims.

I claim:

1. The method of making a tapered propeller blade which consists in bending a sheet-like piece of metal stock having a varying width longitudinally into a blank of tapered tubular formation with opposite side edges of the stock in abutting relationship, closing one end of said blank, and changing the cross-sectional contour of said blank to that desired in the finished product.

2. The method of making a propeller blade from a sheet-like piece of metal stock having a varying width which consists in modifying said stock to a blank of tubular formation with opposite side edges of the stock in abutting relationship, welding the abutting edges of said stock together, closing one end of said blank, and changing the cross-sectional contour of said blank to that desired in the finished product.

3. The method of making a propeller blade blank from a sheet-like piece of stock having a varying width which consists in modifying said stock into tubular formation of varying diameter with opposite side edges in abutting relationship, welding said side edges together, and closing one end of said blank.

4. The method of making a propeller blade from a sheet-like piece of metal stock having a main portion and an end portion of tapering width which consists in bending said stock longitudinally into a tubular blank having a main portion of generally cylindrical formation and an end portion of tapering formation, closing the smallend of said tubular blank, and modifying the cross-sectional contour of said blank to the cross-sectional contour desired in the finished product.

5. The method of making a propeller blade from a sheet-like piece of metal stock having a main pc'tion and an end portion of tapering width which consists in bending said stock longitudinally into a tubular blank with the opposite edge portions of said stock in abutting relationship and having a main portion of approximately cylindrical formation and an end portion of hipering formation, welding the abutting edges of said stock together, closing the small end of said tubular blank, and modifying the cross-sectional contour of said blank to the cross-sectional contour desired in the finished product.

6. The method of making a propeller blade from a sheet-like piece of metal stock having a main portion and an end portion of tapering width which consists in bending said stock longitudinally into a tubular blank having a main portion of approximately cylindrical formation and an end portion of tapering formation, welding the edges of said stock together, closing the small end of said tubular blank, and modifying the cross-sectional contour of said blank to the cross-section contour desired in the finished product with the welded edges of said stock located in a predetermined position in said blade.

7. The method of making a propeller blade from a sheet-like piece of metal stock of uniform thickness and having a non-uniform width which consists in bending said stock longitudinally into a tubular blank of non-uniform diameter and uniform wall thickness with the edges of the stock in abutting relationship, welding said edges together, closing the small end of said blank, and modifying the cross-sectional contour of said blank to the cross-sectional contour desired in the finished blade with said welded edges located in a predetermined location relative to the leading edge of said blade.

8. The method of making a propeller blade from a sheet-like piece of metal stock of uniform thickness and having a non-uniform width which consists in bending said stock longitudinally into a tubular blank of non-uniform diameter and uniform wall thickne s with the edges of the stock in abutting rela ionship, welding said edges together, closing the small end of said blank. and modifying the cross-sectional contour of said blank between die parts with the welded edges thereof located substantially midway between the lateral edges of the concavities of said dies so as to bring the blank to the desired finished contour and to position the welded edges of the stock substantially midway between the leading and trailing edges of the blade.

9. The method of making a propeller blade from a sheet-like piece of metal stock of uniform thickness and having a non-uniform width which consists in bending said stock longitudinally into a tubular blank of non-uniform diameter and uniform Wall thickness with the edges of the stock in abutting relationship, welding said edges together, closing the small end of said blank, modifying the wall thickness of said blank, and modifying the cross-sectional contour of said blank to the cross-sectional contour desired in the finished blade with said welded edges located substantially on the axis of said blade.

10. The method of making a propeller blade blank from a sheet-like piece of metal stock having a main portion of gradually tapering width and an end portion of radically tapering width which consists in bending said stock longitudinally into a tubular blank with the opposite edge portions of said stock in abutting relationship and having a main portion of gradually tapering formation and an end portion of radically tapering formation, welding the abutting edges of said stock together, machining said blank to bring the wall thicknesses of the main and radically tapered end portions to different predetermined dimensions, and closing the small end of the tubular blank.

11. The method of making a propeller blade blank from a sheet-like piece of metal stock of uniform thickness and having a non-uniform width which consists in bending said stock longitudinally into a tubular blank of non-uniform diameter and uniform wall thickness with the edges of the stock in abutting relationship, welding said edges together, machining said blank to bring the wall thickness to tapering formation with the minimum thickness at the smaller end of said blank, and closing the small end of said blank.

12. The method of making a propeller blade blank from a piece of sheet metal stock of uniform thickness and having a non-uniform width which consists in bending said stock longitudinally into a generally tapered tube having uniform wall thickness with the edges of said stock in abutting relationship, welding said edges together, machining said tube to bring the wall thickness to tapering formation with the minimum thickness at the small end of said tube, and closing the small end of said blank.

13. The method of making a propeller blade blank from a piece of sheet metal stock of uniform thickness and having a non-uniform width which consists in bending said stock longitudinally into a generally tapered tube having uniform wall thickness with the edges of said stock in abutting relationship, welding said edges together, machining said blank externally to equalize the perimeters of successive crosssections thereof with the perimeters of corresponding cross-sections of the desired finished product, and closing the small end of said blank.

14. The method of making a propeller blade which consists in forming a tubular blank of circular cross section and non-uniform diameter from a planular blank having widths at successive cross-sections substantially equal to the inner peripheries of the finished product at corresponding cross-sections, closing the small end of said tubular blank, and changing the crosssectional contour of said tubular blank to that desired in the finished product.

15. The method of making a propeller blade which consists in forming a generally tapered tubular blank of circular cross-section from a planular blank having widths at successive cross sections substantially equal to the inner peripheries of the finished product at corresponding cross-sections, machining the exterior of said tubular blank to bring the perimeters of successive cross-sections thereof to the dimensions desired of the corresponding cross sections of the finished product, closing the small end of said tubular blank, and changing the cross-sectional contour of said tubular blank to that desired in the finished product.

16. The method of making a tubular propeller blade blank which consists in providing a planular piece of stock of generally tapered formation having widths at successive cross-sections substantially equal to the desired lengths of the inner peripheries of corresponding sections of the finished product, forming said tapered stock into a generally tapered tube with the opposite edges of the stock in abutting relationship, welding the abutting edges of the stock together, machining the exterior of said tube to predetermined dimensions, and closing the small end of said tube.

17. A propeller blade blank including a planular sheet of metal of uniform thickness and tapering in width over at least a portion of the length thereof symmetrically relative to the longitudinal center line thereof, at least a portion of the side edges of the sheet being curved and the widths of successive cross-sections of said blank being substantially equal to the circumference of the inner peripheries of corresponding sections of a desired blade.

18. The method of making a propeller blade blank from a sheet-like piece of stock having a non-uniform width which consists in modifying said stock into a tubular formation of non-uniform diameter and with opposite side edges of said stock in abutting relationship, welding said side edges together, and hammering the ridge formed on the tubular blank during welding of said edges into conformity with the contour of the inner and outer peripheries of said tube respectively. I

19. A propeller blade blank including a sheetlike piece of metal stock having at least a portion of its width tapering symmetrically relative to the longitudinal center line thereof toward one end along a curved path, the widths of said blank at successive transverse cross-sections being substantially equal to the inner peripheries of corresponding sections of a desired blade.

20. The method of making a tapered tubular propeller blade blank which consists in first forming a sheet-like piece of stock having a tapered end portion of varying widths at successive sections equal to the desired inner peripheral circumferences of corresponding sections in the blank, bending said stock longitudinally into a tubular blank in such a manner as to bring laterally opposite edge portions thereof together in abutting relationship, permanently fixing said side edges together, and closing the small end of the tubular structure.

21. The method of making a tapered tubular propeller blade blank which consists in first forming a sheet-like piece of stock having a tapered end portion of varying widths at successive sections equal to the desired inner peripheral circumferences of corresponding sections in the blank, bending said stock longitudinally into a tubular blank in such a manner as to bring the laterally opposite side portions of said stock together, welding said side edges together, hammering the excess metal at said welded edges so as to improve the grain structure thereof and to bring the welded portion of the tubular structure to the wall thickness thereof, and closing the extremity of the tubular blank at which the tapered end portion of the stock is located.

22. The method of making a tubular propeller blade blank from a sheet-like piece of stock which consists in bringing one end portion of said piece of stock to tapered formation, modifying said stock into a tubular structure of varying diameter with laterally opposite edge portions thereof engaged together, permanently fixing said edge portions together, and closing the extremity of said tubular structure at which the tapered end portion of said stock is located.

23. The method of making a propeller blade from a sheet-like piece of stock which consists in bringing one end portion of said piece of stock to a tapered formation, modifying said stock into a tubular structure of varying diameter with laterally opposite edge portions engaged together, permanently fixing said edge portions together, closing the extremity of said tubular structure at which the tapered end portion is located and compressing said tubular structure to blade shape.

24. The method of making a propeller blade from a sheet-like piece of metal stock having a main portion of gradually tapering width and an end portion of radially tapering width which consists in bending said stock longitudinally into a tubular blank with the opposite edge portions of said stock in abutting relationship and having a main portion of gradually tapering formation and an end portion of radically tapering formation, welding the abutting edges of said stock together, machining said blank to bring the wall thicknesses of the main and radically tapered end portions to different predetermined dimensions, closing the small end of said tubular blank, and modifying the cross-sectional contour of said blank to the cross-sectional contour desired in the finished product.

25. The method of making a propeller blade from a sheet-like piece of metal stock of uniform thickness and having a non-uniform width which consists in bending said stock longitudinally into a tubular blank of non-unifoorm diameter and uniform wall thickness with the edges of the stock in abutting relationship, welding said edges together, machining said blank to bring the wall thickness to tapering formation with the minimum thickness at the smaller end of said blank, closing the small end of said blank, and modifying the cross-sectional contour of said blank to the cross-sectional contour desired in the finished product.

26. The method of making a propeller blade blank from a sheet-like piece of stock having a non-uniform width which consists in bending said stock longitudinally into a generally tapered tube with the edges of said stock engaged together, permanently fixing said edges together, machining said tube to bring its wall thickness to tapering formation with the minimum thickness at the small end of said tube, and closing the small ,10 end of said tube.

JOHN SQUIRES. 

